Automatic cleaner for sparking styluses



April 10, 1951 c. L. BOYAJIAN HAL 5 5 AUTOMATIC 0mm FOR SPARKING STYLUSES Filed Dec. 26, 1947 Their Attorney Patented Apr. 10, 1951 AUTOMATIC CLEANER FOR SPARKING STYLUSES Clement L. Boyajian, George R. Rule, and Herbert M. Dimond, Schenectady, N. Y., assignors to General Electric Company, a corporation of New York Application December 26, 1947, Serial No. 794,076

1 Claim.

This invention relates to electric recorders having a sparking stylus and more particularly to apparatus for cleaning the stylus tip.

A principal difficulty encountered in attempts to design continuous recording apparatus using electric spark recordin paper is the accumulation of carbon on the sparking stylus tip. The accumulated carbon will ignite, drop off on the paper, and set it afire. The object of our invention is to provide apparatus to periodically clean the stylus tip, thus making such continuous recording practicable.

The features of our invention which are believed to be novel and patentable'will be pointed out in the claim appended hereto. For a better understanding of our invention, reference is made in the following description to the accompanying drawing in which Fig. l is a plan View of one form of our invention in which the electric circuits are represented schematically, Fig. 2 is a section along the line 2-2, Fig. Land Fig. 3 is an elevation of another form of our invention. Like reference characters refer to like parts throughout the drawing.

Referring now to Figs. 1 and 2, a voltage to be recorded is applied between terminals l, and responsive thereto a voltage-measuring recording element 2 positions the tip of a stylus 3 upon a sheet of electric spark recording paper 4. In the drawing the stylus is shown in the cleaning position. When recording the stylus tip rests upon the paper. A conventional sparking circuit 5 produces electric sparks between the stylus tip and the metal table 6 upon which the paper is supported. These sparks pass through the recording paper and leave a series of visible marks thereon which is a record of the recorded voltage. When our cleaning apparatus is used these marks may be spaced closely enough together to give a substantially continuous record. Without cleaning apparatus, such close spacing would result in prohibitively rapid carbon accumulation on the stylus tip. The sparking circuit is energized by electric power from a commercial line, or other convenient electric source, applied through terminals 1.

A small rotary brush 8, preferably a fine wire brush, is placed to one side of the recording paper as shown. In the drawing this brush is placed to the left of the paper, but it may be placed to the right without changing the principle of our invention. A second rotary brush 9 is placed as shown to have a point of circumferential contact with brush 8. Preferably the two brushes overlap about /32 inch. The axis of brush 9 is at an angle of about 45 to the axis of brush 8. Brush 8 is a driven brush rotated by a small electric mo- .2 tor I0, and brush 9 is an idler brush rotated by its contact with brush .8. Preferably the brushes rotate in the respective directions indicated by arrows on the drawing. A stylus raiser l l,'plalceid as shown, is adapted to guide the stylusintbthe cleaning position when the stylus is moved to the extreme left as hereinafter explained, so that the stylus tip, which extends downward from the stylus arm as shown in Fig. 2, is positioned be tween the two rotary brushes at their point of contact.

Periodically, preferably once every 10 to 20 minutes, a timing switch I! removes the recorded voltage from the recording element and applies thereto a voltage, obtained from a battery l3 or other voltage source, of such magnitude and polarity that recording element 2 swings stylus 3 to the extreme left into the cleaning position shown in Fig. 1. For example, this may be accomplished by a voltage which is reversed in polarity with respect to the recorded voltage. At the same time, timin switch I2 applies electric power from terminals 1 to motor In so that brushes 8 and 9 are rotated, thus cleaning the stylus tip, and preferably deenergizes the sparking circuit by disconnecting it from the electric power source. Cleaning is continued for approximately three seconds, at the end of which time the timing switch removes the reverse voltage and reapplies the recorded voltage to the recording element, reapplies power to the sparking circuit, and preferably removes the power from motor Ill. The apparatus then continues recording until time for the next cleaning operation. The entire cleaning operation interrupts the recording for no more than five seconds.

By providing two brushes 8 and 9 set at an angle as shown, the stylus tip is forced from between the brushes at the end of each cleaning operation by the rotation of the brushes, since each brush exerts a pressure on the stylus directed away from the brush axle and the resultant pressure is in a direction to force the stylus from between the brushes, so that danger of the stylus becoming caught in the brushes is eliminated.

In Fig. 3 a form of our invention is shown which is adapted for use with an endless belt type recorder. Referring now to this figure, an endless belt I4 is supported by a driven wheel [5 and an idler wheel 16. Three stylus tips H are positioned on the endless belt as shown, so that one stylus tip is in contact with the electric recording paper [8 at all times. A recording element 20 is adapted to rotate wheel [5 and thereby position tips l'l responsive to the recorded voltage or other measurement. A sparking circuit produces sparks between tips I! and metal table I9 to produce a record of the recorded voltage on the paper as hereinbefore described. Element 20 may be a small electric motor responsive, through suitable control and amplifying means, to the voltage output of a Selsyn positioning system, which may comprise a Selsyn transmitter positioned by the quantity to be recorded and a Selsyn transformer positioned by the recorder, adapted to generate an error voltage proportional to a difference in position between the transmitter and the recorder.

A preferably stationary brush 2| is positioned above the endless belt so that whenever a stylus tip moves past the brush it comes in contact therewith and the tip is cleaned. Periodically, preferably once every 10 to-20 minutes, the timing switch applies to element 20 a voltage which causes belt H! to move continuously in one direction forapproximately three seconds. This may be accomplished by applying to element 20 a voltage strong enough to override the error voltage generated by the Selsyn positioning system, or alternatively the error Voltage may be disconnected so that a smaller voltage applied to motor 2|] will cause continuous rotation. During this three-second interval each of the stylus tips I! passes beneath brush 2| and is cleaned thereby.

Th timing switch may also be adapted to deenergize the sparking circuit during cleaning.

In accordance with the patent statutes We have described the principleof our invention together with the apparatus which we now consider to represent the best embodiment thereof, but we wish 0 Number 4 it to be understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What we claim as new and desire to secure by Letters Patent of the United States is:

In an electric recorder having a sparking stylus positioned by a recording element, apparatus to periodically clean the stylus tip comprising a driven rotary brush, an electric motor adapted to rotate said brush, an idler rotary brush having a point of circumferential contact with the driven brush and having its axis at an angle of substantially degrees to the axis of the driven brush, a stylus raiser adapted to guide the stylus into the cleaning position with its tip between the two brushes at their point of contact, and a timing switch adapted to periodically interrupt the recording and apply a voltage to the recording element, to swing the stylus into the cleaning position.

CLEMENT L. BOY AJIAN.

GEORGE R. REDE.

HERBERT M. DIMOND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date OBrien Mar. 20, 1943 Wise et a1. July 6, 1948 Finch Mar. 22, 1949 'Iribble Sept. 6, 1949 

